The present invention relates to hit error rate (BER) checkers.
The eye viewer in a receiver has an ability to observe the eye diagram of a receiver (RX) equalization output. Such an eye viewer, for example, may be used in a high speed serial interface (HSSI) receiver. A receiver of an integrated circuit (IC) is generally integrated with the IC. Similarly, the eye viewer in the receiver is also integrated with the IC. Such an eye viewer is referred to as an on-die or on-chip eye viewer. The eye viewer in the receiver provides several benefits. First, the on-chip eye monitor can work like a scope to probe the internal high-speed nodes which cannot be observed by probing external pins. Second, the eye diagram output by the eye-viewer shows the RX equalization results. This allows for adjusting the amount of equalization to achieve the desired eye diagram. Additionally, the on-chip eye monitor enables one to diagnose and debug HSSI devices without probes and oscilloscopes in field.
The BER checker monitors for data errors of sampled data received from the eye viewer. The BER checker may check for cyclic redundancy check (CRC) errors for unknown data patterns or it may check BER for known data patterns. This may be done to test or debug a device. It may also be used with idle or training sequences, such as “K” or “D” data packages or combinations thereof.
However, in some devices, e.g., in the Stratix® IV GX or GT devices available from Altera® Corporation of San Jose, Calif., in order to perform BER checking on the data output by the eye viewer, the data from the eye viewer is sent to the device core via the deserializer. In these devices, soft intellectual property (IP) in the device core is used to determine the BER. A contour (or multiple contours) of the data eye can be generated based on a threshold BER (or multiple BERs). As a result of sending the data from the eye viewer to the device core via the deserializer for BER checking, BER checking and the clock data recovery (CDR) circuitry share the deserializer. This prevents the use of the eye viewer for BER checking without interrupting the normal operating RX data path. Furthermore, only one out of two data sets can be fed to the soft IP BER checker.
Embodiments of the present invention arise in this context.